Bundy -
you would be wise to call each airline you use if you are not familiar with that airline's restrictions. Depending on what plane you are traveling on, there are different max sizes/weights of carryon that are allowed. There are huge differences between a MD-80 and a 767 overhead compartments. It's worth 5 minutes to save lots of aggravation.
That's one of the reasons I use the same airline/plane size each time; it cuts down on the possible future hassles. Airline travel is one of the most complex/likely delayed modes of transportation in the World. An ounce of prevention....
also, what can go wrong, will likely go wrong...
DayTrader